Windows Media Player (at least the tested 12 version from Windows 7) is unable to play m3u playlists with more than 101 http- streaming entries. Mediaplayer tells you that the playlist can't be opened because of some issues with another computer. This is totally wrong, it's just a cheap excuse to hide this bug in Windows Media Player. If you want to play more than 101 songs at once, please use another Mediaplayer, like VLC. It has a lot more features, does simply it's job and is probably more secure.